LiPo thoughts

[Rex R]

in the past month(or so) I've seen a number of folks complaining about their lipos not living up to their expectations etc. etc., well before the beer gets too watered down lets see what we are getting for our hard earned cash. for a 2s2p setup comprised of 4000mah cells we get; 6000mah of usable power that comes in a package that weighs roughly 13 oz,. I've been told that they deliver like an 8cell nimh pack(weight 18 oz.) for voltage. for amps at a sustainable level of 26c(13c per pack) thats over 100 amps for over 3 minutes! maybe its not the 'killer' 200-300 amp packs some folks think they want, but I think I can live with it.

[SJFE]

OH my god LIPOS...Did you know they can explode with out warning and level a city block!!!! Bad bad bad lipos. I figuered I'd get that right out of the way in this thread before token drama post.

[Rex R]

LOL you noticed that I very carefully mentioned no names, or brand names, or how some folks have been having er shall we say 'technical difficulties' with an older battey tech...:). just wanted to point out that even with derating them to more realistic levels, LiPo's represent an advance in power systems.

[sjslhill]

It all depends on what your doing. I have heard that some professional N2 mono setups are pulling 80 constant amps, in this case you need 10,000mah and 20C. Figure out how many amps your going to pull in a constant and go from there.

30 amps needs a 50 to 60 amp constant LiPoly pack to last a long time. I look forward to hooking up the DPR on my Super Vee and see what it does. I'll then test some LiPoly in it. I think everyone needs to parallel in order to keep from over discharging their packs.

thanks,
Steve

[SJFE]

I look forward to hookin it up in mine also:D

[Rex R]

last graph I saw of a sv amp draw had peaks of roughly 60amps was averaging 35-40amps(iirc)

[sjslhill]

If it peaks 60 amps, my 12C packs will be pushed even in parallel. You have to remember though that watts = voltage x current, the higher the voltage the lower the current levels needed. 14.8V of LiPoly should be better than 14.4V of NIMH

[Doby]

I'll be needing some soon for my V24 mod running a LMT 3080, I'll be looking for around 37V, 10,000 mAh .

[sjslhill]

Send me an e-mail and I'll get you a quote if your interested. sales@battlepack.com

[ice329]

I will let you know next week... have a few 3600 lipos coming from Steve/BattlePack. I got my pencil out and did some figuring. His 3600
12cConstant/16c bursts lipos should be fine. If I had a charger that could charge 4 cells I would have went with 2 of his 14.8 volt pack and would have enough juice for a long long time. Since my charger only will do a 3 cell lipo I got the 7.4. I really want to see a set of lipos in the white boat. Next week I will post some more info. He mentioned that a low volt cutout, not sure if the SV ESC has one or not so I will guage the run time gradually to see how long I can run on the pack without discharging it to low.

[SJFE]

Buy a stand alon voltage cut off. I'm almost posotive the SV ESC don't have one.

[Doby]

The SV27 speed controller does NOT have a LiPo cuttoff.

[Rex R]

oops my bad. data log was for an h & m viper running a super vee motor and esc.
thread here http://www.rcgroups.com/forums/showthread.php?t=633493
rex

[sjslhill]

Yes, we know that......



The SV27 speed controller does NOT have a LiPo cuttoff.

[Doby]

BattlePack;
I sent you an E-Mail here for a quote , when you get a chance , I'd appreciate it .

[ice329]

Would this be it? or something differnt. Tell me more I catch on quick..sorry for all the questions

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXPGM8&P=7

[SJFE]

Mr BattlePack sir...;) ..Did you ever order any of the cut offs? I remember you posted one a month or so ago.

[sjslhill]

I sent you an e-mail back....


BattlePack;
I sent you an E-Mail here for a quote , when you get a chance , I'd appreciate it .

[Doby]

Have not rec'd it yet

[sjslhill]

PM sent, not sure why e-mail did not work

[sjslhill]

No I have not, I was planning on some capacity test runs, but I should get one. ;)


Mr BattlePack sir...;) ..Did you ever order any of the cut offs? I remember you posted one a month or so ago.

[sjslhill]

Someone asked me a question using a PM.....and I'll share the answer.

You can use a Power Supply to charge liPoly packs, however, it must be the following.

4.2V per cell and 1C Max current rate.

example

A 7.4V 4,000mah pack would need a 8.4V, 4 amp switching power supply. As the voltage gets close to 8.4V, the current rate drops. This is how it works.

IT MUST BE SWITCHING!!!!!!!!

[ice329]

Here is a page from the MRC977 Op manual. I posted it for 2 reasons one is so you can see how it says to charge Lipo's since were on the subject.

The other reason is Can some explain to me the paragraph E, on telling capacity. I dont understand it. If you know please use a example of a 4500 MAH battery pack

http://i110.photobucket.com/albums/n103/ice0329/e.jpg

[sjslhill]

Sounds like a discharge of 1/5 amps at the end or C/5

[sjslhill]

What would be good is for Pros and non pros to share LiPoly setups with everyone and make a sticky thread that everyone could read. I know that we have Pros here and I wish they would share more info for everyone. By pros I mean racers that travel and compete on a national level.

thanks,
Steve

[SweetZ28]

Hi i have the 977 you do a discharge and then charge to show capacity ..but i don't think this is 100% acurate...also some guy's don't like the 977 because they say it don't charge lipos in the standard way of consistant current consistant voltage (cc/cv) But many use it and have no problems i charged a few lipos on mine and 2 at one time on it and it never gave me a problem.
But i also have the Ice charger and it has cc/cv lipo charge mode and i mostly charge lipos on it and i never had a problem with the ICE to.

[ice329]

Asked MRC about the Capacity check. Basically discharge the packs and charge them to 120-125 then, take the battery MAH capacity divide it by 5 then discharge at theat rate. So a 4500 mah battery divided by 5 comes out to 900 so it would be discharged at .9 amps. It sounds logical now but I reread that paragraph many times and it makes sense now but didnt last night.

[SJFE]

Well you just asked...Lets see who offers up the information. I would be shocked if some one who is racing and winning tell the potential competition how to level the playing field. But stranger things have happened. One thing we may have to take into is there may not be the "right" setup yet. There arent even and district wide races even posted in #1 yet. As a matter of fact the electric schedule was listed as "TBD" and now is missing from the page all together. One more reason I am not bothering with any events this summer.

[ice329]

Last night I pulled out my little Lipo packs from my planes. I have 2 packs one I suspected a long time ago it wasnt to good and the other was real good. I wanted to test out the MRC Superbrain 977 on Lipo's. I discharged both packs at 4 amps, the one I suspected was bad was... the other had 1724 MAH still in it after 5 months of sitting, there both 1800's. I set the 977 to charge the Lipos at .05c wich was .9 amps. The pack I suspected got warm so I took it off knowing it was bad. The other pack charged really nice. As it approched the 1800 mark I watched it charge for the last few min, watching the voltage. It shut off at 8.37 volts and had 1867MAH. I was impressed for the first charge of Lipos. Just for kicks I discharged that pack again and tha pack held really high(good) voltage right up till the last few MAH's.

[sjslhill]

Store LiPoly at 50-70% charged capacity, not 100%

[ice329]

Thanks steve, when I got the plane and batterys I had no clue about Lipos. I prob wrecked the one I mentioned was bad. I ran that thing down till the prop on the plane didnt even move. I just didnt know... I rather have learned on these little lipos packs then your good ones for the boat. I will dump half the charge out of the plane pack. Thanks

[SweetZ28]

Hi Ice329 i have 977 make sure and i say this again make sure when you charge lipos on the 977 that you select on the desplay CELL even after you start lipo charge after you set the settings because sometimes after you start charging and select the desplay CELL it won't say lipo if it does this stop charging the pack!

always go through the menu with the display after you start lipo charging to the CELL on the display and duble check and make sure it says lipo in the display.

[ice329]

Your right sweet... The guys at MRC stressed to me to select the number of cells and then start the charge from that screen and very imprtant to watch for the word LIPO. I think I know why, prob because if you dont choose the number of cells the charger thinks it a six cell pack because of the voltage. If that the only reason some people dont like it, I can live with it. After I got it a while I will really know if I like it or not, right now..so far so good.

[SweetZ28]

even after you select 2 cell and press start scroll through the display to CELL and make sure it says lipo if it don't stop charge.

[ice329]

I will be very consious of that, thanks... You like the charger otherwise?

[SweetZ28]

Yes it a good charger i also have the Ice and i used that for the lipos but recently i started giving the 977 a try...good thing about the 977 you can charge 2 batteries at one time.

[ice329]

The guys at Tekin recomended it. I was shoping around and I really wanted the double charging capability. Everyone like differnt things.

[ice329]

Just received a set of Li Po's from BattlePack today. I got two 7.4V 3600 12c/16c packs. Put the Deans on them and got right on the MRC 977. The charger, charged them perfect. In the ICE Rocket for a test run they went, so did the GPS. Wow they are nice. Strong solid power threw the entire run. The boat feels light and agile. I GPS the boat with a CF45 at 31MPH. Pretty good considering I GPSed the same setup with 7 cell packs and got 32.8. The packs at the end of the run were 110-112 degrees.

I need to get a low Volt cut off anyone know what one I need?

Also how important is a balencer. Do I need one?

[SweetZ28]

novak makes some
www.teamnovak.com

[ice329]

Would I use one on each battery or would it be one for the whole system. I saw the cut offs but wasnt sure if it was one for the 4 cells of the two batteries together like before the esc or I needed two 2 cell cutoffs on individual cells.

[SweetZ28]

Hi I am not sure maybe somebody can help you out ...hows the boat wired

[sjslhill]

Get a blinky for balancing, that's what I use.

[ice329]

OK Steve I will be adding the binky to my brothers order, will call or email. I might have to give him my packs because his boats going to him in NJ on about the 21st. If his are not done and to me by then I will send him mine and take his. He will luck out getting matched packs and I get his... hehehe

[sjslhill]

When the boss says we are taking off some time, we do it. The Boss (Sarah is the wife as well)